SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5a16dec5137979715416129f4068ae93d2cf6b7b878822d51fb4239168a0f3be' 
  AND token = 'KJrrqow94HdJBLfDzmcnzzLRt/ZQwANLliuJ5u/r6Gk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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