SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15a506eea0bf7a8640d4ad9d6fe67c5bda45fe1e5fac06fbedfe3e4a3541de62' 
  AND token = 'Nz7gLupKSInqvh8BrPmI1CiiG1ixfuA5gYuwYNicrKc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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