SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ffe918281fcaee4e8e897af3b6767fd69e49c4cb7f3ed2d0c5c994cdcb516a1c' 
  AND token = 'V8js1XetTB1FDaYPZ7LN9cd+Ob7RlYPPhvn1zNaRark=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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