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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a50a11fcb84d964cd526c1b637d99d5e200b3e51e7045ae686c7da897c397359' 
  AND token = 'WFLxG6BOsyriJP0ZasHOpEcam+5KFbfMQeOL5HpwabU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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