SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8e5189f386d650675dddd76756a2283a3ab66c2344ab425922f88d3da1dac683' 
  AND token = 'zV87FgSPO+hCLViMNY16zbaebkfqpRdwymOV5id4NMc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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