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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21b5a737f513b4d1c5203ec350bc40f8c421f7e7011daa99e7781c194f41cf15' 
  AND token = 'ux+P+3WhNp1+Ga2CCvFjDmqjxs/aFLLwTlpl1GsItVk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00040

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}