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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd6ed0968350df117979b362add2334d84d5071766f12b92e8bb50c63d0d3af73' 
  AND token = '293uZUnB2CLpPE74ghxXyngQB3EGgDc3d2S1Zmtk4rI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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