SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5b344147b3438282972ad0b1de2b6c69e67c58f47f1951026463d88513c7ebfb' 
  AND token = '8r6PDDz6pezmPMcF2b+CYVlV53s+iU8sxMNkjCHWj/E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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