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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ef4ae1dc4d1009fa080c50ee3fd522a74827d7c678e6ccb62af6bce575bb755' 
  AND token = 'nKji2NU6oEkCaSgq8JtbLX1+aSAzsffEFLyHKjujJzo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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