SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1eb57126b7179d42f91809d49338b62f8936b0b825c822837e042c611e615f59' 
  AND token = '8vFQ0DtnjXjWWJBJUXeM/Dv9vbb1V5yRvKDsCmxB+g4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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