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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9c170b3e0168527dc4f6a3d21645602c45bdc80215be064d305dfbbc25b441d' 
  AND token = 'z/+W5XlvCHiJCWYnDfNMwyxDL4COLK+HdNUj1/Ld3Wo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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