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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f56e9cf0cf1755bd1558e5a1ae0208dbd1a4740ff8840df4bbc75b1ad6f4a1b' 
  AND token = 'GoY9+EtiD/uBnStQhbVEy9HX3FC/wiHMHenSKqCUxWw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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