SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3400fb3aee8f543cbdac63478b50f92f95fef77d26bb97e74d8c4d20254882f' 
  AND token = 'BaJgJIV+sWwEWKusw2JUwOPJahPGvjVUneXdZMNPTwk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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