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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8c783cbd87938d1445ecc947341eead9de958dc5bd427c11a668106df8ae035' 
  AND token = 'nU+r4UKqwPnklTQCTuFIoHZ15oXqPMbivRCGCYj82dk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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