SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a2c58349378e7b6c5db4445fade373c327af981b71912818e0bd9daf0f97231d' 
  AND token = 'qtnPewv+Dhubqc6dhBDg9JW1LbndMimhjs9/cKdJqoE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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