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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76c383829a71e4e75291bc53683a48578da8840900e745e212e699d721ac434d' 
  AND token = 'TH7e7O5wXcf3NB75BQkGTOmoSPKQ1cHTAynLrwNYFUw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}