SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'db3b934e053e24b626d4233db4ea00313509085141e9adcdc5da11f05670f941' 
  AND token = 'usvbhBfa6mlBX5WoF/CCBr0XXij3LjiX3lLpKhwOQG0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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