SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '77a73c3186ff699d4c984c6236acccd30f573ebdb5bf429031e3dc1b0effa7a1' 
  AND token = 'JWbjJZ9qKil8ZFc8RiuFdh/r9hxB0KUCldvpJIvL4nY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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