SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51a35edc6cc6e3420d77bb3cfb9f0b02e13925c5d3f259b9a696a7f125495e4b' 
  AND token = '+HgFWPKvqaUNJVQLDcmGT282CtLPq//thZtFscb6+3g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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