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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9c8da96984f663992b11e90818b0e800e002f085a63ae61bbc6ef86a14ded05' 
  AND token = 'rxYc6E/I1ikLxpl7Kh8Rz3tUUTzR1iKWKCFMWFrfblc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}