SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5244a714cf3e73da25cae0f4afe21f691e30dc7916a37da07950de8403407238' 
  AND token = 'N3oDLRbUEH87HRVqAc+polMZ0SMXnabArjlm3oAmGiI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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