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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a4dbb2c0e763cccc8012d8d51d18613f8abe40555d42d1c466f8a9ba52c4fd6' 
  AND token = 'Js8H4kCHpN9py2gzC1ViMzaba6ll9CJHWmEiQGAN/Nk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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