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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9e82162e18ed067911446b2d718f221df6884ac8ff38055662a8388c2da90ce5' 
  AND token = '4NdbUFdBGLs9TUVtIlHxq8kqQwRLofExtIrPdGw2/R4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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