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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '251da444f264042f0f5149d66984cfc1108db637b932c5e8f0d177e6df2300a4' 
  AND token = '4pmWQG6K9krZ1Q8kGcEfMhISzMuj2co2BcdxOkZr32E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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