SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f99634e617f6df64981fffc16d2c0085010401e988913a0d125fe971b58d3eb' 
  AND token = '2aXfbTzif2vDtfuek9MR7SshACSfYpqcfhZdAIAF9ho=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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