SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21dde0541aac03e6182a4f6660998d782379c388242d3b42ba182eb9f5731e50' 
  AND token = '6TIqAhThwlzfMgqo9gdXNzY6rNnWXecyL+sOSJDDkCQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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