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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a2fbdcde9fedc2a13c1f6be251a80e697ddc91ad7eecf6de4896df2a4f950bfd' 
  AND token = 'UWXyDGV15B1b+/BFGfeI//xSkWqjeHYz+nI6dml4qWk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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