SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '877250b2d621e6a77b765da3e3dcaa1dd9e22cd808a82364138fe7cd6707419b' 
  AND token = 'b6TBADADS7waAQOhSrwCVjrihBe/m23HrXtTSP7a3VM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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