SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8bdf82949f2489c3bb0d4c60943a1fbfd4858345631d1f58753f8b9808aebd23' 
  AND token = 'YYmOEuQKHVwtTjlm4/EmR0yJ+QGcNnVr9xUM0Ku1ugQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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