SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cbe4cdfb2363c5801c056c741738c7d9f77a147412984854416d0939ca7a4cd2' 
  AND token = 'K6nRgh9Ph/d2Wt0qxXGx4wSF0/HGOcq75AyztFR69Mk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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