SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c255445c131bde98312f07f3e4306fea8cae2182515f629faf6724b0cd3fc498' 
  AND token = '6G+Cs3yCZHxnFfoKQ+J68ZJrXIVAvbw4YPfrDl+CbYE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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