SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5ea88fb1ae61256d256baa994839a12b5f3c3e17b9d998162f1cc7ee4983792' 
  AND token = 'BKN+/cKEqMC3R2Btevs8QjfHvHJ/gzVY021aiH6/iiQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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