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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5542a4c67c1f07bbdb230080c0b952312796d1a314c33965819f934f7b481ae3' 
  AND token = 'nkObr+apejTZlb/ys//gOypWwxap7p2+9fT+EhzF3To=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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