SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd5c23874a501331927511267be9eec04a54eb5213971abf60afe6c88d03a649d' 
  AND token = 'dDbsy7fiJb4lk1zthjLsSPEeFgTBxxt7AwWeAKbDXLs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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