SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6cd2bf16a53d22d080051ad0a1c77077aef84d7edecdc0670235c013ddd05f49' 
  AND token = 't5uBfMr9E/X818CdAscT7i+7Fscc5CvbNiI+Kmk4YPg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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