SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '519fa49125263d237a0c5ae54d7952da3f8649f833b71589a6321826433f4b0b' 
  AND token = '+ZheV0CRLLTV0290wHWEROlbRKaGxzIZzin5gY5qhKQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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