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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a242e76ef22682df906c06feb1ed06ed807cae794ac4010504a6fc3dcb1ce942' 
  AND token = 'QlFXXA85aWvn8sBf6e5YvB0fCg/+r2CngqAOzfh9gNk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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