SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a103a5533c1237caea884a4da3333248937fce67ac16aa93019e0628e37c926d' 
  AND token = 'bPTGvRORVqWPWClDFTIxDT7uPQFPYujFiB+4w/hiJbg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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