SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c6969f3e59e1fad57ac047baee12356679dd1d123ef845a870706ff40b608158' 
  AND token = 'RjF69AqIIT3mQir/SKs5gUIK1f2nfr14QtoPhoVmdI8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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