SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50ecc4606facfb1f61b0336f08b37c12a04466cde4678ef9db191dcdc4cad7c2' 
  AND token = '7k9Pu9x1gblq1Lb2+I0xmnQwHQGXTLSng4vFz92JBIw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00013

JSON explain

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