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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '720755253359fff79683633eebaf5de1c7c8e938cba7233c0a47f5207273af92' 
  AND token = '6GeeTCPxWVttXPjTORXIzaUk+fkqmv2wKjEQmtkDqEY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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