SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '12a2f42265f2eae0b775da9934373d1d16d52e5fe8610cb6085728c778262caa' 
  AND token = '9gAxEbsTCnUjQPGYHrl7qiVP9NSLHZorUq5/+Mmmczo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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