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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f34af00030f2426e53e7c8f6f0d9b125dc80c883c1baa3adc87775208f23c51' 
  AND token = '90/SaOUVDLntBFFkBv8UFySqnwcJG8b/7NamM8gm2q4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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