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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8d6cdc2bc0b3f1332431c51dfea666ea2721e92d07f43c3e54ecbfb5fa6fa43' 
  AND token = 'xdLXDgPM1JjdYMhDHAeSuu6Ogtcp234UcVD9pm6iLLg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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