SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fb88e6165f0a59ba87a78c5012460103f78c7abf50bf4954c7a779059965540e' 
  AND token = 'rFBdbYpwUHrDz8nwDHBvcdY8RZG5UQCXGfI53JnFt7M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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