SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75e7a2abb7072e03c4f9345a093c02498f2a75fc1f8d80ce0e903637c56f5f4d' 
  AND token = '6TJnn5jRQDnpPn1ix0k7BrgpUDnRJyVRwFeWQG0Wz+8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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