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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1d21b3db6ba88352ef4b0cde84579b484e400942689acc1b9f9a81bdf3b9b341' 
  AND token = '1hv3eEbUEYf56lupEHNerrJUwK8pEH8ELCTVSy5UvpM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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