SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39d352004683c58d92047c2184b1b24b019a4af1ed46a74df3ca63afa8f03c51' 
  AND token = 'x6c+/sBMrucHt2nuf67h6UC7CBzSGNFcEDKW2mpROKc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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