SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3d242ac544ebc79545923b4a1018f28b61aeb562a25293e13ec313822544f70e' 
  AND token = '2vceiqEJFobSID9EKgd26UwcKeVhMLHIkk2FEOvcYWw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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