SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b492c37def0433aa0ec6b985a9a0b4f9f1432f7d61334f0f33037a2caf3b517a' 
  AND token = 'DOoAgzPYK0IZrrfc9FcJ9berkPPPkOIySVrwLurMl6o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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