SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8739d4d2cfc6d6794c6f45e728d5f66ad1ed3d0a711cc9e9adc65838e794653' 
  AND token = 'Bgg4EmsZwEBb53ZHVRk9ZLLmrsScVjYwdsINKv0ezlQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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