SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8b3560a3b73d58f097249762c6975e7203e995766cf58e377454aab13550579' 
  AND token = 'FlHusHEA/d5a51h9WEvvzF51ZuXUoBWOjOnYXIxlB5M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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