SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15fb244502509cdad0658d67ccc83a701e3bf8d516321f4d38dd62d99277adea' 
  AND token = 'Q30/BKB8wgX2VERA2FI0Y2Mh7tGZG7GIcPqlAs/C3xQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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