SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21c757c74ba404692a8ce8536b3fb2a5a485649d64ad1b7da88ddff44354bbb9' 
  AND token = 'IZ3v/Tgd5su6SLzyXL+vFGfuwhp8w2MOPEXxPcx2lTY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00046

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}