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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3f2cc54acd67071c1de9e96a1b444eed59994cd71c93cfc427b17e13418dd47' 
  AND token = '/sM1WelDZRyKQlkyyHRLOUb1wgMJmztDDj1DqEYo/Cg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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