SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b624dce5c22cd35194a4354db3f1d5583c6746d32e5f8201b72795d6694aa2ba' 
  AND token = 'rSkAH1Dsv2BFwfiPuosmaxzuhHC88gOtCcqgvXhM8LM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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