SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71a20d4c5553d04280bb0e0ad2618fce8ac05b8ab13973e932f2b6c2985ff225' 
  AND token = 'DVVBvFQYS4Ug/y5kD7Cs/LhdzkZrFDiJBW34W7HMhYE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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