SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f39da5ae3207585f1d1caab9b9f6e5c5a83e25e58574283d76fc068488fd577' 
  AND token = '+v11zhB0NYuP1sRPNXbQCAAmPRWpcTsC9+Lf20/yKh0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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