SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd21943a088387b52d4125a11699dbd9a1346bfcc4e3436648b33be1f15f9fc43' 
  AND token = 'aZFESwPsAJPQdO0m5Ln4hTdKo3oU8J94XRk0PSs+DGw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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