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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '49276bc819950306ef382df390443673362d5c03c2ef53bb2b597e9634572f47' 
  AND token = '+ex1UN4epXiA7OuVq7lbFnvz1il7pJgshr/0E47m9lU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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