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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '520798ecd6f093500954193b0fe2d223415ed5927f1aa709cd7e3d3a35da51c2' 
  AND token = 'CtsNCDxkaNJOBuIgpvUonsHGEpwabQsdqMil1d2Dkps=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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